A dobby which is connected to a weaving machine controls on one side patternlike the final position of the frames on the weaving machine, however, it must on the other side also develop the forces to move the controlled or read-in frames from one position, for example the lower shed, into another position, for example the upper shed. Many forces must be overcome thereby, which in turn depend partly on the speed of the frame or rotational speed of the weaving machine.
The most important one of these forces is the force for overcoming the mass acceleration of a complete frame and, in the spring release weaving machines, the force for overcoming the draw-back forces which engage the frame, thus spring force plus resistance and weight of the moved frame and spring parts. These forces could be reduced, if on the one hand the weight and on the other hand the force of the spring could be reduced.
A reduction of the weight of the entire frame is generally not desired because the solidity and rigidity of the frame is not to suffer under such a reduction. The frame must be built so strong that it can receive, without any large deformation, the forces which act up on it.
The purpose of the invention is to reduce the forces which are exerted as a reaction by the frame against the draw members.
This is attained inventively in a weaving machine of the above-mentioned type by having elastically expandable, pretensioned draw means engage the end of each heddle for reducing the moved frame mass, the lower end of which draw means is anchored on an abutment.
With this two force reductions can be achieved, namely on the one hand the entire weight of the frame can be reduced considerably without the danger of a reduction in the stability of the frame and on the other hand the operating members only overcome the effective spring force. A further advantage lies in the operational clearance between the heddles and the frame being overcome by the individual springs, namely the heddles stay with the braking movement of the frame. Shocks of the heddles during braking do not occur.